A series of tests of reproductive endocrine function have been carried out on male volunteers in the Baltimore Longitudinal Study on Aging. Cross sectional data have been obtained on androgen, estrogen, and gonadotropin levels in serum. Level of sexual activity is being related to hormone levels. Results show no change with age in serum sex steroid levels in men, but significant elevations of serum gonadotropins. There is a modest decrease in pituitary gonadotropic response to LRH and a small reduction in testosterone secretion in response to chorionic gonadotropin. Sexual activity appears significantly correlated with serum testosterone in men over 60. New work is underway to assess effects of age in metabolic clearance of glycoprotein hormones.